Issue |
Europhys. Lett.
Volume 59, Number 5, September 2002
|
|
---|---|---|
Page(s) | 754 - 760 | |
Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
DOI | https://doi.org/10.1209/epl/i2002-00190-3 | |
Published online | 01 September 2002 |
On the consequences of the uncertainty principle on the superconducting fluctuations well inside the normal state
Laboratorio de Baixas Temperaturas e
Superconductividade Departamento de Física da Materia
Condensada Universidade de Santiago de Compostela -
Santiago de Compostela, E-15782, Spain
Received:
15
April
2002
Accepted:
5
June
2002
We first argue that the collective behaviour of the
Cooper pairs created by thermal fluctuations well above the
superconducting transition temperature, Tc, is dominated by the
uncertainty principle which, in particular, leads to a well-defined
temperature, Tc, above which the superconducting coherence
vanishes. On the grounds of the BCS approach, the corresponding
reduced temperature,
, is estimated to be around
0.55,
i.e., above
coherent Cooper pairs cannot
exist. The implications of these proposals on the superfluid
density are then examined using the Gaussian-Ginzburg-Landau
approximation. Then we present new measurements of the thermal
fluctuation effects on the electrical conductivity and
on the magnetization in different low- and high-Tc
superconductors with different dopings which are in excellent
agreement with these proposals and that demonstrate the
universality of
.
PACS: 74.20.-z – Theories and models of superconducting state / 74.20.De – Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) / 74.40.+k – Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.)
© EDP Sciences, 2002
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